Bovine Respiratory Disease

Bovine Respiratory Disease is one of the most common respiratory diseases in cattle. It is often called "shipping fever"  and is the most common cause of illness and death in feedlot cattle in Australia. It can also be seen in extensively managed beef herds, particularly calves and weaners.

Production losses are felt not only in deaths of severely affected livestock but in reduced average daily gains and lower feed conversion efficiency. One Australian study of 2468 feedlot cattle with an average induction weight of 340kg showed that the daily gain of cattle affected with BRD was on average, 700g lower per day than that of unaffected cattle.

What is Bovine Respiratory Disease?

Bovine Respiratory Disease (BRD) is more accurately a ‘disease complex’ rather than one bug that causes disease.

For BRD to occur there generally needs to be three things: stress + virus + bacteria.

The bacteria that causes BRD live in cattle's throats, some may have more than others. The viruses are also carried by the cattle, the most common one of these (IBR) is a herpesvirus (different to the one affecting humans) that lives in the throat of some cattle, just like the bacteria do. There are also a handful of other viruses (including Pestivirus) that have been linked to BRD. The one main factor in BRD development that we can have some control over is stress.

What causes Bovine Respiratory Disease?

BRD is caused by a complex interaction between commensal viruses and bacteria that usually live harmlessly in the respiratory tract of healthy cattle. The disease is usually triggered during or following a stressful period by a viral infection and a subsequent infection of the airways with opportunistic bacteria. This combination of stress factors and infectious agents makes feedlot cattle especially vulnerable.

Many of the same risk factors apply when restocking, especially when using those cattle to strategically graze paddocks in a more intensive situation.

In extensively managed beef herds, stress can be due to:

  • Social stress (weaning and/or social disruption)
  • Comingling (transport, saleyards or mixing of new mobs)
  • Feed or water changes (changes in supplementary feed or increased green lush feed following rain event)
  • Extreme weather (extended rain periods, sudden cold snaps, going from cold nights to warm days, dusty conditions)

Bovine Respiratory Disease is seen most frequently in Autumn and Early Winter.

Bos Taurus (British Breeds) are more susceptible than Bos Indicus (Brahman/Santa Gertrudis type) cattle.

The process of cattle succumbing to BRD is outlined in the diagram below:

Stress factors and mitigation measures

The most common stressors for BRD (and ways to mitigate) are listed below:

  • Weaning – low stress, avoid buying recently weaned cattle where possible
  • Saleyards – the extra transport/yarding increases stress and exposure to viruses
  • Transport – reduce the distance were possible, acknowledge the impact long distance travel will have on your BRD risk
  • Time off feed – proportional to stress, feed hay as soon as they come off the truck to fill them back up
  • Co-mingling or new social groups – one of the biggest factors. Not only are cattle exposed to viruses they’ve never encountered before, don’t underestimate the impact that a change in social group has on stress. Re-establishment of the ‘pecking order’ is a major stress.
  • Handling and yarding – do the minimum required, minimise time in yards, if you do not know the previous handling conditions of the cattle, keep it as quiet and low stress as possible, ie. Don’t use dogs in yards as those cattle may have never seen a dog before!
  • Weather – big fluctuations in temperature (rather than minimum temperatures – except for maybe in the dead of winter) will increase the amount of BRD. If bringing cattle down from Northern Australia this may have an impact too.
  • Water changes – switching from bore to rain or particularly from rain to bore can have a big impact on water intake. Keep this in mind and ask questions where possible about water source the cattle are used to. Not easy to change but will increase your likelihood of BRD.

Clinical signs of Bovine Respiratory Disease

Know what to look for with BRD in cattle:

  • Fever (up to 42°C)
  • Watery nasal discharge progressing to a thick mucoid nasal discharge
  • Depression and lethargy
  • Lack of appetite
  • Cough
  • Rapid, shallow breathing
  • Unwillingness to move, standing with neck extended

BRD can present as pneumonia but may occasionally result in severely affected stock death. The lungs are a perfect home for these bacteria and they replicate very quickly and cause a huge amount of damage – pus, inflammation, scar tissue, reduced amount of oxygen in the blood. This process causes a high fever, depression, reduced feed intake and respiratory signs.

Initial signs may just a bit of a watery nasal discharge and maybe a soft, tentative cough. As the infection gets worse you’ll hear a loud, harsh cough and sometimes see a cloudy nasal discharge. At this stage you will notice they are dull, will stand on their own, are taking really short and shallow breaths and may have their neck outstretched to aid breathing.

To see any of these signs though you need to spend 5 or 10 minutes a day watching them. Signs of Bovine Respiratory Disease can be subtle and it’s really important to pick any issues up early as the disease can progress rapidly in a couple of days. If you see any signs you’re concerned about, please contact your local vet.

Bovine Respiratory Disease Treatment

Treatment of BRD involves anti-inflammatories to help reduce the fever and antibiotics that are targeted to killing the specific bacteria that are causing the problem.

Please DO NOT use some old penicillin that you’ve had in the fridge for years, it’s not the right antibiotic to use and will only prolong the course of disease.

Preventing Bovine Respiratory Disease

The good news is that there are some vaccines that can be used to help prevent BRD. They are not a silver bullet (you still need to try and reduce those stressors as much as possible) but are a great tool in your BRD toolkit.

Some recommendations for vaccines are as follows:

When buying cattle (especially younger cattle) from multiple sources and co-mingling

  • Bovishield MH (a vaccine for one of the most common bacteria involved), or
  • Bovilis MH + IBR (two doses but protects against the main virus as well as one of the most common bacteria involved)

Cattle that you have bought as above that are likely going to go to a feedlot

  • Bovilis MH + IBR (a vaccine for the most common virus and one of the most common bacteria involved), requires 2 vaccinations, minimum 14 days apart but up to 180 days apart. Feedlots will often pay a premium for cattle that have been vaccinated but please check first as it may depend on when the cattle are vaccinated.
  • Bovishield MH (helps protect against one of the most common bacteria involved)

Homebred cattle, no introductions, likely going to a feedlot

  • Bovilis MH + IBR (usually 4 weeks prior to feedlot entry – but check with your buyer

Start of a BRD outbreak

  • Rhinoguard – intranasal vaccine for IBR virus, 1mL up each nostril (as opposed to 2mL in one nostril), faster protection than the Bovilis MH + IBR or Bovishield MH but more handling. Rhinoguard can be used in conjunction with the single shot Bovishield MH.

Middle to end of BRD outbreak

  • Debatable as to usefulness of vaccination as exposure and immunity have likely occurred.
  • Better off focusing on pulling and appropriate treatment of sick animals.

If you have any questions about preventing or diagnosing BRD please contact your local vet to discuss. Remember to ask lots of questions about the stock you are purchasing and ensure your agent is keeping in mind the risk factors outlined above to avoid a BRD outbreak in your herd.

Adapted from content by district vets, Erica Kennedy and Katelyn Braine

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